Thanks @LeLev for the great support. If you guys could please direct me for basics stuffs related to syntax, I would appreciate. As a pre-requisite I really need to understand how the things work before putting the hands on it.

great! That works. With that I can spare the toggle functions at all. Thanks!

You could also simplify this a little: void MainWindow::menuToggled() { auto widget = (container->currentWidget() == menuWidget) ? mdiContainer : menuWidget; container->setCurrentwidget(widget); }